Add data-testid to test relevant elements (fixes #244)

Change-Id: Id908e38f01e426543ed98975544204a9a632294d
diff --git a/templates/failure.html.ep b/templates/failure.html.ep
index e1f6fb3..c644e3a 100644
--- a/templates/failure.html.ep
+++ b/templates/failure.html.ep
@@ -9,5 +9,5 @@
 <p class="no-results"><%= loc('notIssued') %></p>
 
 % if (stash('err_msg')) {
-<p class="no-results"><%== loc(stash('err_msg'),stash('err_msg')) %></p>
+<p class="no-results" data-testid="error-message"><%== loc(stash('err_msg'),stash('err_msg')) %></p>
 % }